Device and method for correcting a data error in communication path

Abstract

There are provided a transmission and reception device having a function for correcting a data error in a communication path. In the transmission device, a redundant bit addition unit adds a redundant bit to each data bit which has been divided by one bit by a division unit; and an interleaver performs interleave. The transmission device transmits a signal which has been subjected to FM modulation by an FM modulation unit. In the reception device, a symbol decision unit performs a symbol decision at a Nyquist point for a signal which has been FM-demodulated by an FM demodulation unit; a bit conversion unit performs bit conversion according to the result of symbol decision; and a frame recovery unit deletes the redundant bit added by the redundant bit addition unit of the transmission device, from the bit string de-interleaved by a de-interleaver. Thus, it is possible to surely perform an error correction with a simple configuration even when the communication state is not in a preferable environment.

The invention claimed is: 
     
       1. A transmission device which modulates and transmits transmission data of which a level of importance has been previously determined, comprising:
 a division unit configured to divide (1) a high-importance data string by one bit to generate high-importance bit data each having one bit and (2) a low-importance data string into low-importance bit data each having two bits; 
 a bit addition unit configured to add a fixed value of one bit to each one bit of the high-importance bit data, to generate two bit high-importance bit data; and 
 a modulation unit configured to perform modulation for arranging the two bit high-importance bit data generated and the two bit low-importance bit data to respective symbols based on the two bit data, 
 wherein the fixed value is bit data which is common to, in an arrangement of the symbols, two symbols having a largest Euclidean distance, and 
 a symbol including the high-importance data string is arranged to one of two symbols, among the symbols, having the largest Euclidean distance by adding the bit data having the fixed value. 
 
     
     
       2. The transmission device according to  claim 1 , wherein the high-importance data string includes flag data. 
     
     
       3. The transmission device according to  claim 1 , wherein the high-importance data string includes bits for error check. 
     
     
       4. The transmission device according to  claim 1 , wherein the high-importance data string includes bits for error correction. 
     
     
       5. The transmission device according to  claim 1 , wherein the quantity of the high-importance data string is less than the quantity of the low-importance data string. 
     
     
       6. A transmission method of a transmission device which modulates and transmits transmission data of which a level of importance has been previously determined, comprising:
 dividing a high-importance data string by one bit to generate high-importance bit data each having one bit; 
 dividing a low-importance data string into low-importance bit data each having two bits; 
 adding a fixed value of one bit to each one bit of the high-importance bit data, to generate two bit high-importance bit data; and 
 performing modulation for arranging the two bit high-importance bit data generated and the two bit low-importance bit data, to respective symbols based on the two bit data, 
 wherein the fixed value is bit data which is common to, in an arrangement of the symbols, two symbols having a largest Euclidean distance, and 
 a symbol including the high-importance data string is arranged to one of two symbols, among the respective symbols, having the largest Euclidean distance by adding the bit data having the fixed value.